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l(No'lwodel.)

" W. B. FARWELL.

l DRY ORE GONGENTRATOR. No. 218,325. Patented VMay 29, 1883.

Z/z'fnessss.'

UNITED STATES PATENT OFFICE.

WIIILARD B. FARWELL, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR, BY

DIRECT AND MESNE ASSIGNMENTS, OF FIVE-EIGHTHS TO JOHN LANDER AND I. IVI. TAYLOR, OF SAMEV PLACE. d j

lDRY-OREGONCENTRATOR.

SPECIFICATION forming part of Letters Patent No. avsaadatea May 29, 1.883.

' Application mea July 17,1882. No model.)V Y

'To allwhom it may concern."`

Be itknown that I, WILLARDB. FARWELL,

a citizen of the United States, at present sojournin g in San Francisco, county of San Francisco, and State of California, have lnade and invented certain new and useful Improvements in Dry-Ore Concentrators; and I do hereby declare that the `following is a full, clear, and exact description of the same, reference being ro had to the accompanying drawings.

My invention relates to certain improvements in ore-concentrating machines of the kind known as dry-ore conccntrators,7 the ore being spread upon a perforate belt or sury face having horizontal progressive motion over a blast or current of air directed upward Aagainst the underside of the` surface and through the perfor-ations thereof, whereby stratication of the particles according to 2o their specific gravity is effected.

The following description explains the nature of -my several improvements and the manner in which I construct, apply, and combine them together with the other parts of a machine or apparatus.

In the drawings herein referred to, Figure l is a vertical longitudinal section through the upper portion of amachine-frame, the traveling belt and its driving-rolls, showing my 3o improvements applied thereto. Fig`12 is a top view of several of the holding-down rollers at and near the `discharge end of the machine.A Figs. 3 and 4 are details of theyieldingcut-off plate.

3 The bed et has motion in one direction from the hopper b tothe discharge end or tail of the machine, passing over the open top of the airchamberic, andV receiving from the bel- -lows oroth'er air-forcing apparatus therein 4o successive blasts or strong impulses of air against its under surface. To counteract this pressure against the under side and the tendencyof the bedto yield and rise with it, I place across the bed, at intervals apart, and

over the working portion of its surface, a number of trundle-bars, D D, having spurs or spoke-like projectionsd d, and centered upon p intles 'e e, having bearings inthe side frames,

so as to revolve freely. Said bars are set at such distance above the bed that the projections d d touch orrnn in close proximity to its surface when it is in horizontalpositiong and. being loosely pivoted` in the side frame, said bars are free to turn as the bed moves along I beneath them. `Sufficient space between the surfacev of the bed andthe bottomlsfof the trundle-bars isafl'orded for the body of ore to l `on the bars D are formed of a number of wire loops orstaples of rectangular shape, WithV their ends let into the body of the bars, and havin g sufficient projection therefrom to touch the ore-bed or run in r close proximity thereto when the bars rotate. Being thus open, and presenting small surfaces to engage with the ore matter, they take into and pass out from it without disturbing theuniformity of the layer or throwing offits particles.l These pron jectionsare to be preferred in place of simple spokes, pins, or other devices presenting ends or points, as the bed is prevented from catching upon and being torn or injured by such projections in this traveling movement. In4 practice I support these trundlabars in separate side rails, e e', so that they can be readily lifted out and removed from the bed. `Thisis shown in Figs. 1 and 2, wherethese side rails are simply set in the frame against cleats or projections placed at either end of the said rails on the main frame. them in place laterally. i

Over and along the sides ofthe bed I place apsE to close the spaces between the sides of the bedandthe sidefames. Theselaps are made of some flexible materialsuch as rubber-` and are fastened to the side frames along the inside. They are wide enough to lap upon portions of the bed-surface beyond the sides. The lapped portion of each is made to lie flatupon the bed-surface, and closely enough to prevent the particles of sand or ore from working in between thesurfaces and escaping into the bellows-chamber beneath. Y

The rollers keep directed each into its proper receptacle, is of novel construction and operation. It is adjustable, and also self-yielding, in its action.

' The cut-off plate Gconsists of a blade placed at the discharge end of the bed, and having an inclined position, or one tangent to the curved surface of the bed where it leaves the horizontal and begins to turn over the drum or roller. It has a beveled front edge, and exf tends across the bed the full width of its working-surface. Its upper surface,being inclined toward the discharge, receives and directs all that portion of ore matter composing the top stratum into the chute l, while the space left between this front edge and the surface of the bed affords outlet for the lowest stratum resting on the moving surface. y

yTo change the height of the plate G it is centered on pivots g g' in the side frames, and a set-screw, J, heldin a bracket, 7c, bears upon the rear end. By turning this screw the position of the edge 'g' of the plate is readily ad- 2 5 justed. A spring, h, of suitable strength', is

bolted at one end to the cross-timber of the frame to press against the front end of the plate, and thus keep the rear end in' contact with the end of the set-screw. This construction likewise gives a self-yielding'capacity to the cut-off plate, by which its front edge will rise and permit any small obstructions-such as lumps or large particles of oremto pass beneath it through the outlet below the edge g. The discharge cannot clog or choke, and is therefore kopt free and clear.

Having thus fully described my invention,

what I claim, and desire to secure by Letters 1. In a dry-ore concentrator, the combination, with a traveling belt, of mechanism distributed at various points along the length of the said belt for the purpose of holding it down against the action of an air-blast from beneath, as set forth.

2. The combination, with the traveling oresupporting surface in a dry-ore concentrator, of the trundle-bars D, constructed and applied to operate substantially asdescribed.

8. In a dry-ore .concentrator, the combination, with the ore-supporting surface, of the adjustable inclined pivoted cut-oft'tplate G, the adjusting means placed on one side of the center pivot, and the yielding means placed upon the other side thereof, whereby a capacity for yielding when the character of the progressing ore makes itnecessary is imparted to the plate G, substantially as hereinset forth.

4;. The combination of the plate G, pivoted at its center, g, with the spring h, placed above said plate and in front ot' the pivot,"and the a'djustingscrew J, placed'above the plate and the plate is kept taut against the screw, un-

less the force of the spring is overcome by the bearing upon it back of the pivot, whereby 

